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Longer Concentric Action Increases Muscle Activation And Neuromuscular Fatigue Responses In Protocols Equalized By Repetition Duration

Lacerda Lucas T.; Costa, Cinara G.; Lima, Fernando V.; Martins-Costa, Hugo C.; Diniz, Rodrigo C.R.; Andrade, André G.P.; Peixoto, Gustavo H.C.; Bemben, Michael G.; Chagas, Mauro H.
The Journal of Strength & Conditioning Research: Post Acceptance: July 19, 2017
doi: 10.1519/JSC.0000000000002148
Original Research: PDF Only

The aim of this study was to investigate the impact of protocols equalized by the repetition duration but composed of different concentric and eccentric durations on muscle activation and neuromuscular fatigue. Seventeen males with previous experience in resistance training performed 3 training protocols (A - 2s con : 4s ecc; B - 3s con : 3s ecc; and C - 4s con : 2s ecc) with the Smith machine bench press exercise, all with 3 sets, 6 repetitions, 3 minutes' rest, and 60% of 1RM. The normalized root mean square of the electromyographic signal (EMGRMS) and mean frequency electromyography (EMGMF) for pectoralis major and triceps brachii muscles were calculated for 2nd and 5th repetitions in each set. The results showed an EMGMF decrease across the repetitions accompanied by a progressive increase of the EMGRMS across the repetitions for all protocols and muscles. The EMGRMS was higher in Protocol C when compared with Protocol A and B for pectoralis major. The EMGMF was lower in Protocols B and C than in Protocol A for pectoralis major throughout the sets and repetitions. A higher EMGRMS and a lower EMGMF were observed in Protocols B and C compared to Protocol A for triceps brachii, solely in the 5th repetition . In conclusion, training protocols conducted with the same repetition duration, but with different concentric and eccentric durations, produce distinct muscle activation and neuromuscular fatigue responses, in which performing longer concentric durations could be the more appropriate strategy to increase muscle activation and neuromuscular fatigue.

Author correspondence: PhD. Mauro Heleno Chagas Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy Federal University of Minas Gerais. Av. Antônio Carlos, 6627, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil. e-mail: Telephone: (+55 31) 3409-7443 Fax number: (+55 31) 3409-7443

This study received support from the FAPEMIG; CAPES (Brazil); and PRPq da Universidade Federal de Minas Gerais.

Copyright © 2018 by the National Strength & Conditioning Association.